Showing papers by "Noriyoshi Ishii published in 2009"

Theoretical Foundation of the Nuclear Force in QCD and its applications to Central and Tensor Forces in Quenched Lattice QCD Simulations

Abstract: We present full accounts of a method to extract nucleon-nucleon (NN) potentials from the Bethe-Salpter amplitude in lattice QCD. The method is applied to two nucleons on the lattice with quenched QCD simulations. By disentangling the mixing between the S-state and the D-state, we obtain central and tensor potentials in the leading order of the velocity expansion of the non-local NN potential. The spatial structure and the quark mass dependence of the potentials are analyzed in detail.

Lambda-nucleon force from lattice QCD

Abstract: We study the $\Lambda$-nucleon ($\Lambda N$) force by using lattice QCD The Bethe-Salpeter amplitude is calculated for the lowest scattering state of the $\Lambda N$ so as to obtain the $\Lambda N$ potential The numerical calculation is twofold: (i) Full lattice QCD by using 2+1 flavor PACS-CS gauge configurations with, $\beta=19$, corresponding to the lattice spacing of $a=00907(13)$ fm, on a $32^3\times 64$ lattice A set of parameter $(\kappa_{ud},\kappa_s)=(013770,013640)$ is used, which corresponds to $m_\pi\approx 300$ MeV and $m_K\approx 594$ MeV The spatial lattice volume corresponds to (286 fm)$^3$ (ii) Quenched lattice QCD with $\beta=57$, the lattice spacing of $a=01416(9)$ fm, on the $32^3\times48$ lattice Two sets of hopping parameters $(\kappa_{ud},\kappa_s)=(01665,01643),(01670,01643)$ are used The spatial lattice volume is (45 fm)$^3$ For the full QCD, we find that the $\Lambda p$ has a relatively strong (weak) repulsive core in the $^1S_0$ ($^3S_1$) channel at short distance, while the potential has slight attractive region at medium distance The lowest scattering energy in the finite lattice volume is calculated; Slightly negative values obtained in both spin channels For the quenched QCD, we find that the results are qualitatively in agreement with those in the full QCD calculation

Towards the equation of state in 2+1 flavor QCD with improved Wilson quarks in the fixed scale approach

Abstract: We report on the status of our study towards the equation of state in 2+1 flavor QCD with improved Wilson quarks. To reduce the computational cost which is quite demanding for Wilson-type quarks, we adopt the fixed scale approach, i.e. the temperature T is varied by N_t at fixed lattice spacing. Since the conventional integral method to obtain the pressure is inapplicable at a fixed scale, we adopt the "T-integral method", to calculate the pressure non-perturbatively. Reduction of the computational cost of T=0 simulations thus achieved is indispensable to study EOS in QCD with dynamical quarks.

Towards the equation of state in 2+1 flavor QCD with improved Wilson quarks in the fixed scale approach

Abstract: We report on the status of our study towards the equation of state in 2 + 1 flavor QCD with improved Wilson quarks. To reduce the computational cost which is quite demanding for Wilsontype quarks, we adopt the fixed scale approach, i.e. the temperature T is varied by Nt at fixed lattice spacing. Since the conventional integral method to obtain the pressure is inapplicable at a fixed scale, we adopt the "T-integral method", to calculate the pressure non-perturbatively. Reduction of the computational cost of T = 0 simulations thus achieved is indispensable to study EOS in QCD with dynamical quarks.

Lambda-nucleon force from lattice QCD

Abstract: We study the Λ-nucleon (ΛN) force by using lattice QCD. The Bethe-Salpeter amplitude is calculated for the lowest scattering state of the ΛN so as to obtain the ΛN potential. The numerical calculation is twofold: (i) Full lattice QCD by using 2 + 1 flavor PACS-CS gauge configurations with, β = 1.9, corresponding to the lattice spacing of a = 0.0907(13) fm, on a 323× 64 lattice. A set of parameter (κud ,κs) = (0.13770,0.13640) is used, which corresponds to mπ ≈ 300 MeV and mK ≈ 594 MeV. The spatial lattice volume corresponds to (2.86 fm)3. (ii) Quenched lattice QCD with β = 5.7, the lattice spacing of a = 0.1416(9) fm, on the 323× 48 lattice. Two sets of hopping parameters (κud ,κs) = (0.1665,0.1643),(0.1670,0.1643) are used. The spatial lattice volume is (4.5 fm)3. For the full QCD, we find that the Λp has a relatively strong (weak) repulsive core in the S0 ( S1) channel at short distance, while the potential has slight attractive region at medium distance. The lowest scattering energy in the finite lattice volume is calculated; Slightly negative values obtained in both spin channels. For the quenched QCD, we find that the results are qualitatively in agreement with those in the full QCD calculation.

Hyperon-nucleon forces calculated from lattice qcd

Abstract: We study the hyperon-nucleon (YN) forces by using quenched lattice QCD. The Bethe-Salpeter amplitudes are calculated for the lowest scattering state of the systems so as to obtain the YN potentials. The numerical calculation is twofold: (i) The pΞ0 potentials and scattering lengths are obtained by using lattice QCD with β = 5.7, the lattice spacing of a = 0.1416(9) fm, on the 323 × 32 lattice. Two kinds of ud quark mass are used, corresponding to mπ ≃ 0.37 GeV and 0.51 GeV. The spatial lattice volume is (4.5 fm)3. The scattering lengths obtained from Luscher's formula show that the pΞ0 interactions are both attractive at 1S0 and 3S1 channels, and the interaction in the 3S1 is more attractive than in the 1S0. These attractive forces become stronger as the u, d quark mass decreases. (ii) The pΛ potentials are calculated. The lattice setup is almost same as the former calculation except for the temporal part. The calculation is performed on 323 × 48 lattice. Two kinds of ud quark mass are used, corresponding...